GaN film grown on Si substrate using multilayer AlN/AlxGa1-xN buffer is studied by the low-pressure metal-organic chemical-vapor deposition method. The AlxGa1-xN films with Al composition varying from 1 to 0.66 were used to accommodate the stress induced between GaN and the Si substrate during GaN growth. The correlation of the Al composition in the AlxGa1-xN films with respect to the stress induced in the GaN film grown was studied using high-resolution x-ray diffraction, including symmetrical and asymmetrical omega/2 theta scans and reciprocal space maps. It is found that with proper design of the Al composition in the AlxGa1-xN buffer layer, crack-free GaN film can be successfully grown on 6 in. Si (111) substrates using multilayer AlN and AlxGa1-xN buffer layers. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3385672]